Novel compounds

ABSTRACT

Compounds of general formula (I), wherein R 1  selected from phenyl, pyridinyl, thiophenyl, furanyl, imidazolyl, and triazolyl; where each R 1  phenyl ring and R 1  heteroaromatic ring may optionally and independently be further substituted by 1, 2 or 3 substituents selected from straight and branched C 1 -C 6  alkyl, NO 2 , CF 3 , C 1 -C 6  alkoxy, chloro, fluoro, bromo, and iodo.

FIELD OF THE INVENTION

[0001] The present invention is directed to novel compounds, to aprocess for their preparation, their use and pharmaceutical compositionscomprising the novel compounds. The novel compounds are useful intherapy, and in particular for the treatment of pain.

BACKGROUND AND PRIOR ART

[0002] The δ receptor has been identified as having a role in manybodily functions such as circulatory and pain systems. Ligands for the δreceptor may therefore find potential use as analgesics, and/or asantihypertensive agents. Ligands for the δ receptor have also been shownto possess immunomodulatory activities.

[0003] The identification of at least three different populations ofopioid receptors (μ, δ and κ) is now well established and all three areapparent in both central and peripheral nervous systems of many speciesincluding man. Analgesia has been observed in various animal models whenone or more of these receptors has been activated.

[0004] With few exceptions, currently available selective opioid δligands are peptidic in nature and are unsuitable for administration bysystemic routes. One example of a non-peptidic δ-agonist is SNC80(Bilsky E. J. et al., Journal of Pharmacology and ExperimentalTherapeutics, 273(1), pp. 359-366 (1995)). There is however still a needfor selective δ-agonists having not only improved selectivity, but alsoan improved side-effect profile.

[0005] Thus, the problem underlying the present invention was to findnew analgesics having improved analgesic effects, but also with animproved side-effect profile over current μ agonists, as well as havingimproved systemic efficacy.

[0006] Analgesics that have been identified and are existing in theprior art have many disadvantages in that they suffer from poorpharmacokinetics and are not analgesic when administered by systemicroutes. Also, it has been documented that preferred δ agonist compounds,described within the prior art, show significant convulsive effects whenadministered systemically.

[0007] We have now found that certain compounds not specificallydisclosed by, but included within the scope of WO 98/28270, exhibitsurprisingly improved δ-agonist properties and in vivo potency relativeto compounds disclosed in WO98/28270, when administered systemically.The compounds of the present invention exhibit significant andunexpected increased levels of delta receptor agonism and metabolicstability.

OUTLINE OF THE INVENTION

[0008] The novel compounds according to the present invention aredefined by the formula I

[0009] where each R¹ phenyl ring and R¹ heteroaromatic ring mayoptionally and independently be further substituted by 1, 2 or 3substituents selected from straight and branched C₁-C₆ alkyl, NO₂, CF₃,C₁-C₆ alkoxy, chloro, fluoro, bromo, and iodo. The substitutions on thephenyl ring and on the heteroaromatic ring may take place in anyposition on said ring systems.

[0010] Within the scope of the invention are also pharmaceuticallyacceptable salts of the compounds of the formula I, as well as isomersthereof.

[0011] When the phenyl ring and the heteroaromatic ring(s) aresubstituted, the preferred substituents are selected from anyone of CF₃,methyl, iodo, bromo, fluoro and chloro.

[0012] In a preferred embodiment of the invention, the compounds offormula I are present as the (+)-enantiomer, or as the (−)-enantiomer.

[0013] By “isomers” we mean compounds of the formula I, which differ bythe position of their functional group and/or orientation. By“orientation” we mean stereoisomers, diastereoisomers, regioisomers andenantiomers.

[0014] The novel compounds of the present invention are useful intherapy, especially for the treatment of various pain conditions such aschronic pain, neuropathic pain, acute pain, cancer pain, pain caused byrheumatoid arthritis, migraine, visceral pain etc. This list shouldhowever not be interpreted as exhaustive.

[0015] Compounds of the invention are useful as immunomodulators,especially for autoimmune diseases, such as arthritis, for skin grafts,organ transplants and similar surgical needs, for collagen diseases,various allergies, for use as anti-tumour agents and anti viral agents.

[0016] Compounds of the invention are useful in disease states wheredegeneration or dysfunction of opioid receptors is present or implicatedin that paradigm. This may involve the use of isotopically labelledversions of the compounds of the invention in diagnostic techniques andimaging applications such as positron emission tomography (PET).

[0017] Compounds of the invention are useful for the treatment ofdiarrhoea, depression, anxiety, urinary incontinence, various mentalillnesses, cough, lung oedema, various gastro-intestinal disorders,spinal injury and drug addiction, including the treatment of alcohol,nicotine, opioid and other drug abuse and for disorders of thesympathetic nervous system for example hypertension.

[0018] Compounds of the invention are useful as an analgesic agent foruse during general anaesthesia and monitored anaesthesia care.Combinations of agents with different properties are often used toachieve a balance of effects needed to maintain the anaesthetic state(eg. amnesia, analgesia, muscle relaxation and sedation). Included inthis combination are inhaled anaesthetics, hypnotica, anxiolytics,neuromuscular blockers and opioids.

[0019] Also within the scope of the invention is the use of any of thecompounds according to the formula I above, for the manufacture of amedicament for the treatment of any of the conditions discussed above.

[0020] A further aspect of the invention is a method for the treatmentof a subject suffering from any of the conditions discussed above,whereby an effective amount of a compound according to the formula Iabove, is administered to a patient in need of such treatment.

[0021] Also included within the scope of the present invention, is anynovel intermediate as described in Scheme I hereinafter useful in thesynthesis of compounds of formula I above.

[0022] Methods of Preparation

[0023] The compounds according to the present invention may be preparedby following the synthetic procedure described in Scheme I below. Thisknown procedure is described in Katritsky, A. R., Laji, X. Chem. Soc.Rev., pp. 363-373 (1994), which is hereby incorporated by reference.

EXAMPLES

[0024] The invention will now be described in more detail by thefollowing Examples, which are not to be construed as limiting theinvention.

[0025] The compounds according to Examples 1-3 were prepared byfollowing the synthetic procedure described in Scheme I below.

Example 1

[0026] Preparation of4-[(4-benzyl-1-piperazinyl)(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)methyl]-N,N-diethylbenzamideDihydrochloride (Compound 6)

[0027] (i) Preparation of 2,2-Dimethyl-2,3-dihydro-1-benzofuran-7-ylTrifluoromethanesulfonate (Compound 1)

[0028] 2,2-dimethyl-2,3-dihydro-1-benzofuran-7-ol (19 g, 0.11 mol) andpyridine (18 mL, 0.23 mol) was dissolved in CH₂Cl₂ at 0° C. Triflicanhydride (23 mL, 0.14 mol) was added dropwise. After strirring 1 h at25° C. the mixture was diluted with CH₂Cl₂ and washed with HCl (aq.),dried (Mg SO₄) and evaporated in vacuo.

[0029] Yield 32 g (96%) of compound 1, which did not need purificationbut was used directly in the following step.

[0030]¹H NMR (CDCl₃) δ 1.50 (s, 6H), 3.09 (s, 2H), 6.81 (m, 1H), 7.03(m, 1H), 7.11 (m, 1H), MS (EI) m/e 296, 163, 135, 107.

[0031] (ii) Preparation of Methyl2,2-dimethyl-2,3-dihydro-1-benzofuran-7-carboxylate (Compound 2)

[0032] Compound 1 prepared in the previous step above (32 g, 0.11 mol)was dissolved in DMSO (200 mL), MeOH (100 mL) and Et₃N (34 mL, 0.25mol). Carbon monoxide was passed through the solution 2-3 min, thenpalladium acetate (0.24 g) and dppf (1.1 g) was added and the mixtureheated at 70° C. under CO atmosphere. After 4 h, more palladium acetate(0.10 g) and dppf (0.50 g) was added. After 12 h, EtOAc and water wasadded and the organic phase was washed with HCl (aq.), brine, dried(MgSO₄) and evaporated. chromatography on silica (0-20% EtOAc inheptane) gave 12 g (52%) of compound 2.

[0033]¹H NMR (CDCl₃) δ 1.52 (s, 6H), 3.00 (s, 2H), 3.88 (s, 3H), 6.82(m, 1H), 7.27 (m, 1H), 7.70 (m, 1¹H). MS (EI) m/e 206, 174, 159, 146,131.

[0034] (iii) Preparation of2,2-Dimethyl-2,3-dihydro-1-benzofuran-7-carbaldebyde (Compound 3)

[0035] Compound 2 (5.0 g, 24 mmol) was dissolved in toluene (100 mL) andDIBAL in toluene (33 mL, 1.5 M, 50 mmol) was added at −78° C. undernitrogen atmosphere. After 30 min, the reaction was worked up byaddition of HCl (aq.), the organic phase was dried (MgSO₄) andevaporated in vacuo. The residue was dissolved in CH₂Cl₂ (50 mL) andfinely ground pyridinium dichromate (PDC) (11 g, 29 mmol) was added inportions. The mixture was heated at 40° C. and portions of PDC (1 g) wasadded until reaction was complete. Dilution with heptane, filteringthrough silica and evaporation gave a crude product which was purifiedby chromatography on silica (0-20% EtOAc in heptane) to give compound 3(3.3 g, 19 mmol, 67% from compound 2.

[0036]¹H NMR (CDCl₃) δ 1.54 (s, 6H), 3.03 (s, 2H), 6.88 (m, 1H), 7.34(m, 1H), 7.58 (m, 1H), 10.22 (s, 1H). MS (EI) m/e 176, 161, 147, 130.

[0037] (iv) & (v) Preparation of4-[(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)(hydroxy)methyl]-N,N-diethylbenzamide(Compound 4) and4-[(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)(1-piperazinyl)methyl]-N,N-diethylbenzamide(Compound 5)

[0038] N,N-Diethyl-4-iodobenzamide (compound I) (14 g, 47 mmol) wasdissolved in THF (150 mL) and cooled to −78° C. under nitrogenatmosphere. n-BuLi (21 mL, 2.2 M solution in hexane, 47 mmol) was addeddropwise. Stirring was continued for 30 min at −78° C. The aldehyde(compound 3) (4.1 g, 24 mmol) was added dropwise dissolved in THF (2mL). NH₄Cl (aq.) was added after 30 min. After concentration in vacuo,extraction with EtOAc/water, drying (MgSO₄) and evaporation of theorganic phase, the residue was purified by chromatography on silica to(compound 4) (6.1 g, 17 mmol). After treatment with SOCl₂ (1.5 mL, 20mmol) in dry CH₂Cl₂ (200 mL) at 0 to 25° C. for 1 h, the solvent wasevaporated in vacuo. The residue was dissolved in MeCN (100 mL) andreacted with piperazine (5.8 g, 68 mmol) at 80° C. for 12 h. Afterconcentration in vacuo and chromatography on silica (0 to 15% MeOH inCH₂Cl₂, with 1% NH₄OH) gave (compound 5) (4.9 g, 11 mmol).Dihydrochloride made with HCl (aq) and lyophilization.

[0039] mp 130-40° C. (di HCl salt). IR (KBr, v_(max)) 2982, 2722, 2481,1628, 1450, 1371, 1292, 1140. ¹H NMR (CD₃0D) δ 1.1,1.2 (2m, 6H), 1.36,1.43 (2s, 6H), 2.72 (m, 4H), 2.95 (m, 2H), 3.25 (m, 6H), 3.5 (m, 2H),4.8 (s, 1H), 6.74-7.60 (m, 7H). Anal. (C₂₆H₃₅N₃O₂) C, H, N.

[0040] (vi) Preparation of the Title Compound4-[(4-benzyl-1-piperazinyl)(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)methyl]-N,N-diethylbenzamideDihydrochloride (Compound 6)

[0041] Compound 5 (0.62 g, 1.5 mmol) and triethylamine (0.41 mL, 2.9mmol) was dissolved in MeCN (5 mL) and reacted with benzyl bromide (0.17mL, 1.5 mmol) at 25° C. After 2 h a second portion benzyl bromide wasadded, and after 4 h the reaction was worked up by concentration invacuo and chromatography on silica (0 to 10% MeOH in CH₂Cl₂) to give thetitle compound 6 (0.49 g, 0.95 mmol). Dihydrochloride made with HCl (aq)and lyophilization. MS (ES) 512.08 (MH+).

[0042] IR (NaCl, free amine, v_(max)) 2969, 2806, 2360, 1630, 1451,1368, 1289, 1135 cm⁻¹. ¹H NMR (CDCl₃, free amine) δ 1.1, 1.2 (2m, 6H,amide-Me), 1.36, 1.46 (2s, 6H, Me2C), 2.5 (m, 8H, piperazine-H), 2.92(m, 2H, ArCH2), 3.2, 3.5 (2m, amide-CH2), 3.51 (s, 2H, ArCH2N), 4.62 (s,1H, Ar2CH), 6.72-7.52 (m, 7H, Ar-H). Anal. (C₃₃H₄₁N₃O₂×3.4 HCl) C, H; N:calcd, 6.61; found, 7.19.

Example 2

[0043] Preparation of4-{(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)[4-(4-iodobenzyl)-1-piperazinyl]methyl}-N,N-diethylbenzamideDihydrochloride (Compound 7)

[0044] Procedure as for compound 6. Compound 5 (0.12 g, 0.29 mmol) wasreacted with 4-iodobenzyl bromide (96 mg, 0.32 mmol) for 48 h to givethe title compound 7 (56 mg, 88 μmol).

[0045] MS (ES) 638.24 (MH+). IR (NaCl, free amine, v_(max)) 2969, 2810,1630, 1451, 1288, 1135, 1007 cm⁻¹.

[0046]¹H NMR (CDCl₃, free amine) δ 1.1, 1.2 (2m, 6H, amide-Me), 1.36,1.45 (2s, 6H, Me2C), 2.4 (m, 8H, piperazine-H), 2.94 (m, 2H, ArCH2),3.2, 3.5 (2m, amide-CH2), 3.43 (s, 2H, ArCH2N), 4.62 (s, 1H, Ar2CH),6.73 (m, 1H, Ar-H), 6.94 (d, J=7.3 Hz, 1H, ArH), 7.05 (d, J=8.0 Hz, 2H,ArH), 7.19 (d, J=6.6 Hz, 1H, ArH), 7.25 (d, J=8.0 Hz, 2H, ArH), 7.48 (d,J=8.0 Hz, 2H, ArH), 7.61 (d, J=8.0 Hz, 2H, ArH). Anal. (C₂₆H₃₇Cl₂N₃O₂)C, H, N.

Example 3

[0047] Preparation of4-{(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)[4-(3-pyridinylmethyl)-1-piperazinyl]methyl}-N,N-diethylbenzamideDihydrochloride (Compound 8)

[0048] Compound 5 (0.20 g, 0.47 mmol) was dissolved in MeOH (2 mL) with3-pyridine carboxaldehyde(90 μL, 0.95 mmol) and HOAc (3 μL, 50 μmol).Sodium cyanoborohydride (60 mg, 0.95 mmol) was added at 0° C. andreaction stirred 48 h at 25° C. Reaction was worked up by concentrationin vacuo, extraction (CH₂Cl₂/K₂CO₃(aq)) and chromatography on silica (0to 10% MeOH in CH₂Cl₂) to give the title compound δ (82 mg, 0.16 mmol).Dihydrochloride made with HCl (aq) and lyophilization.

[0049] MS 513.25 (MH+). IR (NaCl, free amine, v_(max)) 2970, 2808, 2360,1631, 1452, 1425, 1290, 1135, 1096, 1009 cm⁻¹. ¹H NMR (CDCl₃, freeamine) δ 1.1, 1.2 (2m, 6H, amide-Me), 1.36, 1.46 (2s, 6H, Me2C), 2.5 (m,8H, piperazine-H), 2.94 (m, 2H, ArCH2), 3.2, 3.5 (2m, amide-CH2), 3.51(s, 2H, ArCH2N), 4.64 (s, 1H, Ar2CH), 6.72-7.66 (m, 9H, Ar-H), 8.44-8.54(m, 2H, Ar-H). Anal. (C₃₂H₄₂Cl₂N₄O₂) C, H, N.

Example 4

[0050] Preparation of4-{(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)[4-(2-pyridinylmethyl)-1-piperazinyl]methyl}-N,N-diethylbenzamideDitrifuroacetae (Compound 9)

[0051] The title compound 9 was prepared by dissolving compound 5 (0.45g, 0.98 mmol) in MeOH (10 mL) with 2-pyridine carboxaldehyde (110 μL,1.18 mmol) and HOAc (3 μL, 50 μmol). Sodium cyanoborohydride (70 mg,1.18 mmol) was added at 0° C. and reaction stirred 48 h at 25° C.Reaction was worked up by concentration in vacuo, extraction(CH₂Cl₂/K₂CO₃(aq)) and chromatography by reverse phase HPLC to give thetitle compound 9,461 mg(63%).

[0052] MS 513.04 (MH+).

[0053] Pharmaceutical Compositions

[0054] The novel compounds according to the present invention may beadministered orally, intramuscularly, subcutaneously, topically,intranasally, intraperitoneally, intrathoracially, intravenously,epidurally, intrathecally, intracerebroventricularly and by injectioninto the joints.

[0055] A preferred route of administration is orally, intravenously orintramuscularly.

[0056] The dosage will depend on the route of administration, theseverity of the disease, age and weight of the patient and other factorsnormally considered by the attending physician, when determining theindividual regimen and dosage level as the most appropriate for aparticular patient.

[0057] For preparing pharmaceutical compositions from the compounds ofthis invention, inert, pharmaceutically acceptable carriers can beeither solid or liquid. Solid form preparations include powders,tablets, dispersible granules, capsules, cachets, and suppositories.

[0058] A solid carrier can be one or more substances which may also actas diluents, flavoring agents, solubilizers, lubricants, suspendingagents, binders, or tablet disintegrating agents; it can also be anencapsulating material.

[0059] In powders, the carrier is a finely divided solid which is in amixture with the finely divided active component. In tablets, the activecomponent is mixed with the carrier having the necessary bindingproperties in suitable proportions and compacted in the shape and sizedesired.

[0060] For preparing suppository compositions, a low-melting wax such asa mixture of fatty acid glycerides and cocoa butter is first melted andthe active ingredient is dispersed therein by, for example, stirring.The molten homogeneous mixture is then poured into convenient sizedmolds and allowed to cool and solidify.

[0061] Suitable carriers are magnesium carbonate, magnesium stearate,talc, lactose, sugar, pectin, dextrin, starch, tragacanth, methylcellulose, sodium carboxymethyl cellulose, a low-melting wax, cocoabutter, and the like.

[0062] Pharmaceutically acceptable salts are acetate, benzenesulfonate,benzoate, bicarbonate, bitartrate, bromide, calcium acetate, camsylate,carbonate, chloride, citrate, dihydrochloride, edetate, edisylate,estolate, esylate, fumarate, glucaptate, gluconate, glutamate,glycollylarsanilate, hexylresorcinate, hydrabamine, hydrobromide,hydrochloride, hydroxynaphthoate, iodide, isethionate, lactate,lactobionate, malate, maleate, mandelate mesylate, methylbromide,methylnitrate, methylsulfate, mucate, napsylate, nitrate, pamoate(embonate), pantothenate, phosphate/diphosphate, polygalacturonate,salicylate, stearate, subacetate, succinate, sulfate, tannate, tartrate,teoclate, triethiodide, benzathine, chloroprocaine, choline,diethanolamine, ethylenediamine, meglumine, procaine, aluminium,calcium, lithium, magnesium, potassium, sodium, and zinc. Preferredpharmaceutically acceptable salts are the hydrochlorides, andbitartrates. The hydrochloride salts are particularly preferred.

[0063] The term composition is intended to include the formulation ofthe active component with encapsulating material as a carrier providinga capsule in which the active component (with or without other carriers)is surrounded by a carrier which is thus in association with it.Similarly, cachets are included.

[0064] Tablets, powders, cachets, and capsules can be used as soliddosage forms suitable for oral administration.

[0065] Liquid from compositions include solutions, suspensions, andemulsions. Sterile water or water-propylene glycol solutions of theactive compounds may be mentioned as an example of liquid preparationssuitable for parenteral administration. Liquid compositions can also beformulated in solution in aqueous polyethylene glycol solution.

[0066] Aqueous solutions for oral administration can be prepared bydissolving the active component in water and adding suitable colorants,flavoring agents, stabilizers, and thickening agents as desired. Aqueoussuspensions for oral use can be made by dispersing the finely dividedactive component in water together with a viscous material such asnatural synthetic gums, resins, methyl cellulose, sodium carboxymethylcellulose, and other suspending agents known to the pharmaceuticalformulation art.

[0067] Preferably the pharmaceutical compositions is in unit dosageform. In such form, the composition is divided into unit dosescontaining appropriate quantities of the active component. The unitdosage form can be a packaged preparation, the package containingdiscrete quantities of the preparations, for example, packeted tablets,capsules, and powders in vials or ampoules. The unit dosage form canalso be a capsule, cachet, or tablet itself, or it can be theappropriate number of any of these packaged forms.

Biological Evaluation

[0068] In vitro Model

[0069] Cell Culture

[0070] Human 293S cells expressing cloned human μ, δ, and ε receptorsand neomycin resistance were grown in suspension at 37° C. and 5% CO₂ inshaker flasks containing calcium-free DMEM 10% FBS, 5% BCS, 0.1%Pluronic F-68, and 600 μg/ml geneticin.

[0071] Membrane Preparation

[0072] Cells were pelleted and resuspended in lysis buffer (50 mM Tris,pH 7.0, 2.5 mM EDTA, with PMSF added just prior to use to 0.1 mM from a0.1 M stock in ethanol), incubated on ice for 15 min, then homogenizedwith a polytron for 30 sec. The suspension was spun at 1000 g (max) for10 min at 4° C. The supernatant was saved on ice and the pelletsresuspended and spun as before. The supernatants from both spins werecombined and spun at 46,000 g(max) for 30 min. The pellets wereresuspended in cold Tris buffer (50 mM Tris/Cl, pH 7.0) and spun again.The final pellets were resuspended in membrane buffer (50 mM Tris, 0.32M sucrose, pH 7.0). Aliquots (1 ml) in polypropylene tubes were frozenin dry ice/ethanol and stored at −70° C. until use. The proteinconcentrations were determined by a modified Lowry assay with SDS.

[0073] Binding Assays

[0074] Membranes were thawed at 37° C., cooled on ice, passed 3 timesthrough a 25-gauge needle, and diluted into binding buffer (50 mM Tris,3 mM MgCl₂, 1 mg/ml BSA (Sigma A-7888), pH 7.4, which was stored at 4°C. after filtration through a 0.22 m filter, and to which had beenfreshly added 5 μg/ml aprotinin, 10 μM bestatin, 10 μM diprotin A, noDTT). Aliquots of 100 μl (for μg protein, see Table 1) were added toiced 12×75 mm polypropylene tubes containing 100 μl of the appropriateradioligand (see Table 1) and 100 μl of test peptides at variousconcentrations. Total (TB) and nonspecific (NS) binding were determinedin the absence and presence of 10 μM naloxone respectively. The tubeswere vortexed and incubated at 25° C. for 60-75 min, after which timethe contents are rapidly vacuum-filtered and washed with about 12ml/tube iced wash buffer (50 mM Tris, pH 7.0, 3 mM MgCl₂) through GF/Bfilters (Whatman) presoaked for at least 2 h in 0.1% polyethyleneimine.The radioactivity (dpm) retained on the filters was measured with a betacounter after soaking the filters for at least 12 h in minivialscontaining 6-7 ml scintillation fluid. If the assay is set up in96-place deep well plates, the filtration is over 96-place PEI-soakedunifilters, which were washed with 3×1 ml wash buffer, and dried in anoven at 55° C. for 2 h. The filter plates were counted in a TopCount(Packard) after adding 50 μl MS-20 scintillation fluid/well.

[0075] Data Analysis

[0076] The specific binding (SB) was calculated as TB-NS, and the SB inthe presence of various test peptides was expressed as percentage ofcontrol SB. Values of IC₅₀ and Hill coefficient (n_(H)) for ligands indisplacing specifically bound radioligand were calculated from logitplots or curve fitting programs such as Ligand, GraphPad Prism,SigmaPlot, or ReceptorFit. Values of K_(i) were calculated from theCheng-Prussoff equation. Mean±S.E.M. values of IC₅₀, K_(i) and n_(H)were reported for ligands tested in at least three displacement curves.Biological data are reported below in Table 1. TABLE 1 Summary ofbiological data. HDelta Rat Brain Mouse Brain MLM RLM Example % % %10000 100000 10000 100000 # HDelta EC50 EMAX EC50 EMAX EC50 EMAX % rem.% rem. % rem. % rem. 3 3.519 19.47 103.1 133.72 92.97 4 3.264 7.38 103.972.59 118.04 144.13 118.5 44.5 93 42.5 90.5

[0077] Receptor Saturation Experiments

[0078] Radioligand Kδ values were determined by performing the bindingassays on cell membranes with the appropriate radioligands atconcentrations ranging from 0.2 to 5 times the estimated Kδ (up to 10times if amounts of radioligand required are feasable). The specificradioligand binding was expressed as pmole/mg membrane protein. Valuesof Kδ and B_(max) from individual experiments were obtained fromnonlinear fits of specifically bound (B) vs. nM free (F) radioligandfrom individual according to a one-site model.

Determination of Mechano-Allodynia Using Von Frey Testing

[0079] Testing was performed between 08:00 and 16:00 h using the methoddescribed by Chaplan et al. (1994). Rats were placed in Plexiglas cageson top of a wire mesh bottom which allowed access to the paw, and wereleft to habituate for 10-15 min. The area tested was the mid-plantarleft hind paw, avoiding the less sensitive foot pads. The paw wastouched with a series of 8 Von Frey hairs with logarithmicallyincremental stiffness (0.41, 0.69, 1.20, 2.04, 3.63, 5.50, 8.51, and15.14 grams; Stoelting, Ill., USA). The von Frey hair was applied fromunderneath the mesh floor perpendicular to the plantar surface withsufficient force to cause a slight buckling against the paw, and heldfor approximately 6-8 seconds. A positive response was noted if the pawwas sharply withdrawn. Flinching immediately upon removal of the hairwas also considered a positive response. Ambulation was considered anambiguous response, and in such cases the stimulus was repeated.

Testing Protocol

[0080] The animals were tested on postoperative day 1 for theFCA-treated group. The 50% withdrawal threshold was determined using theup-down method of Dixon (1980). Testing was started with the 2.04 ghair, in the middle of the series. Stimuli were always presented in aconsecutive way, whether ascending or descending. In the absence of apaw withdrawal response to the initially selected hair, a strongerstimulus was presented; in the event of paw withdrawal, the next weakerstimulus was chosen. Optimal threshold calculation by this methodrequires 6 responses in the immediate vicinity of the 50% threshold, andcounting of these 6 responses began when the first change in responseoccurred, e.g. the threshold was first crossed. In cases wherethresholds fell outside the range of stimuli, values of 15.14 (normalsensitivity) or 0.41 (maximally allodynic) were respectively assigned.The resulting pattern of positive and negative responses was tabulatedusing the convention, X=no withdrawal; O=withdrawal, and the 50%withdrawal threshold was interpolated using the formula:

50% g threshold=10^((Xf+k) _(δ))/10,000

[0081] where Xf=value of the last von Frey hair used (log units);k=tabular value (from Chaplan et al. (1994)) for the pattern ofpositive/negative responses; and δ=mean difference between stimuli (logunits). Here δ=0.224.

[0082] Von Frey thresholds were converted to percent of maximum possibleeffect (% MPE), according to Chaplan et al. 1994. The following equationwas used to compute % MPE:${\% \quad {MPE}} = {\frac{{{Drug}\quad {treated}\quad {threshold}\quad (g)} - {{allodynia}\quad {threshold}\quad (g)}}{{{Control}\quad {{threshold}(g)}} - {{allodynia}\quad {threshold}\quad (g)}} \times 100}$

Administration of Test Substance

[0083] Rats were injected (subcutaneously, intraperitoneally, or orally)with a test substance prior to von Frey testing, the time betweenadministration of test compound and the von Frey test varied dependingupon the nature of the test compound.

Writhing Test

[0084] Acetic acid will bring abdominal contractions when administeredintraperitoneally in mice. These will then extend their body in atypical pattern. When analgesic drugs are administered, this describedmovement is less frequently observed and the drug selected as apotential good candidate.

[0085] A complete and typical Writhing reflexe is considered only whenthe following elements are present: the animal is not in movement; thelower back is slightly depressed; the plantar aspect of both paws isobservable.

[0086] (i) Solutions Preparation

[0087] Acetic acid (AcOH): 120 μL of Acetic Acid is added to 19.88 ml ofdistilled water in order to obtain a final volume of 20 ml with a finalconcentration of 0.6% AcOH. The solution is then mixed (vortex) andready for injection.

[0088] Compound (drug): Each compound is prepared and dissolved in themost suitable vehicle according to standard procedures.

[0089] (ii) Solutions Administration

[0090] The compound (drug) is administered orally, intraperitoneally(i.p.), subcutaneously (s.c.) or intravenously (i.v.)) at 10 ml/kg(considering the average mice body weight) 20, 30 or 40 minutes(according to the class of compound and its characteristics) prior totesting. When the compound is delivered centrally: Intraventricularly(i.c.v.) or intrathecally (i.t.) a volume of 5 μL is administered.

[0091] The AcOH is administered intraperitoneally (i.p.) in two sites at10 ml/kg (considering the average mice body weight) immediately prior totesting.

[0092] (iii) Testing

[0093] The animal (mouse) is observed for a period of 20 minutes and thenumber of occasions (Writhing reflex) noted and compiled at the end ofthe experiment. Mice are kept in individual “shoe box” cages withcontact bedding. A total of 4 mice are usually observed at the sametime: one control and three doses of drug.

1. A compound according to formula I

where each R¹ phenyl ring and R¹ heteroaromatic ring may optionally andindependently be further substituted by 1, 2 or 3 substituents selectedfrom straight and branched C₁-C₆ alkyl, NO₂, CF₃, C₁-C₆ alkoxy, chloro,fluoro, bromo, and iodo. The substitutions on the phenyl ring and on theheteroaromatic ring may take place in any position on said ring systems;as well as pharmaceutically acceptable salts and isomers thereof.
 2. Acompound according to claim 1, wherein the optional substituent(s) onthe aromatic or the heteroaromatic ring(s) is selected from anyone ofNO₂, iso-butyl, CF₃, methoxy, methyl, or chloro.
 3. A compound accordingto claim 1 or 2, selected from any one of4-[(4-benzyl-1-piperazinyl)(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)methyl]-N,N-diethylbenzamidedihydrochloride (compound 6);4-{(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)[4-(4-iodobenzyl)-1-piperazinyl]methyl}-N,N-diethylbenzamidedihydrochloride (compound 7);4-{(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)[4-(3-pyridinylmethyl)-1-piperazinyl]methyl}-N,N-diethylbenzamidedihydrochloride (compound 8); and4-{(2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl)[4-(2-pyridinylmethyl)-1-piperazinyl]methyl}-N,N-diethylbenzamideditrifuroacetae (compound 9).
 4. A compound according to any one ofclaims 1-3, which compound is present as the (+)-enantiomer.
 5. Acompound according to anyone of claims 1-3, which compound is present asthe (−)-enantiomer.
 6. A compound according to any of the precedingclaims, in form of its hydrochloride, sulfate, tartrate or citratesalts.
 7. A compound according to any of claims 1-6 for use in therapy.8. A compound according to claim 7, wherein the therapy is painmanagement.
 9. A compound according to claim 7, wherein the therapy isdirected towards gastrointestinal disorders.
 10. A compound according toclaim 7, wherein the therapy is directed towards spinal injuries.
 11. Acompound according to claim 7, wherein the therapy is directed todisorders of the sympathetic nervous system.
 12. Use of a compoundaccording to formula I of claim 1 for the manufacture of a medicamentfor use in the treatment of pain.
 13. Use of a compound according toformula I of claim 1 for the manufacture of a medicament for use in thetreatment of gastrointestinal disorders.
 14. Use of a compound accordingto formula I of claim 1 for the manufacture of a medicament for use inthe treatment of spinal injuries.
 15. A pharmaceutical compositioncomprising a compound of the formula I according to claim 1 as an activeingredient, together with a pharmacologically and pharmaceuticallyacceptable carrier.
 16. A method for the treatment of pain, whereby aneffective amount of a compound of the formula I according to claim 1 isadministered to a subject in need of pain management.
 17. A method forthe treatment of gastrointestinal disorders, whereby an effective amountof a compound of the formula I according to claim 1, is administered toa subject suffering from said gastrointestinal disorder.
 18. A methodfor the treatment of spinal injuries, whereby an effective amount of acompound of the formula I according to claim 1, is administered to asubject suffering from said spinal injury.